2 a : ultimate reality that underlies all outward manifestations and change b : practical importance : MEANING , USEFULNESS <the ⋯ billwhich will be without substance in the sense that it will authorize nothing more than a set of ideas ― Richard Reeves>

3 a : physical material from which something is made or which has discrete existence b : matter of particular or definite chemical constitution c : something (as drugs or alcoholic beverages) deemed harmful and usually subject to legal restriction <possession of a controlled substance > < substance abuse>